The present invention relates to a bonding method of a first structure and a second structure. More precisely, the invention relates to a bonding method by direct bonding of surfaces, What is meant by “direct bonding” is spontaneous bonding resulting from placing two surfaces in direct contact, i.e. in the absence of an additional element such as a glue, a wax or a brazing. The bonding is mainly caused by the Van der Waals forces originating from the electronic interaction between the atoms or molecules of two surfaces, the hydrogen bonds due to the surface preparations or the covalent bonds established between the two surfaces. Bonding by molecular adhesion can also be referred to.
Conventionally, a high bonding strength (i.e. with a separation energy of more than 3 J·m−2, a measurement made by inserting a blade at the bonding interface) is sought for while not involving any heat treatment of the bonding interface at high temperature, typically more than 100° C.